This invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing a novel sulfonated polyester resin, and process for the preparation thereof. In embodiments, there are provided in accordance with the present invention, toner compositions comprised of certain sulfonated polyester resin particles and pigment particles comprised of, for example, carbon black, cyan, magenta, or yellow, thereby providing for the development and generation of black and/or colored images. In embodiments, there are provided in accordance with the present invention processes for the preparation of toner and developer compositions, and more specifically emulsion aggregation toner processes. In embodiments, the present invention relates to processes which comprise the preparation of a sulfonated polyester resin represented by the formula ##STR2## derived from at least one dicarboxylic acid or diester component, at least one diol component, and at least 0.5 mole percent to about 8 mole percent of a sulfonated difunctional monomer, and wherein M is an ion such as hydrogen, ammonium, lithium, sodium, potassium, an alkali earth or a metal ion; R and R' are as illustrated herein such as alkyl, aryl, oxyalkylene and the sum of o+n equals 100 percent, and o is preferably from about 0.5 to about 8 mole percent. In another embodiment, the present invention relates to an in situ process for the preparation of toner compositions which comprises homogenizing a polymer, especially a sulfonated polyester resin utilizing a Gaulin homogenizer, available from APV Gaulin Incorporated, containing an aqueous solution containing an ionic and nonionic surfactant at a temperature of from about 120.degree. C. to about 170.degree. C., subsequently homogenizing the mixture and generating suspended particles of about 0.05 micron to about 2 microns in volume diameter; aggregating the resulting microsuspension with a mixture of cationic surfactant, pigment and optional charge enhancing additives in an aqueous solution; followed by coalescence of the aggregates by heating thereby providing toner particles with an average particle volume diameter of from between about 3 to about 21 microns. The present invention is thus directed to a toner composition comprised of a sulfonated polyester and the economical preparation of toners without the utilization of the known pulverization and/or classification methods, and wherein toners with an average volume diameter of from about 3 to about 21 microns can be obtained. The resulting toners can be selected for known electrophotographic imaging and printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process comprised of homogenizing a molten resin, preferably a sulfonated polyester resin, exhibiting a melt viscosity of from about 10 poise to about 10,000 poise in a sealed vessel heated of from about 120.degree. to about 170.degree. C. containing an aqueous solution comprised of at least two surfactants, wherein one surfactant is nonionic and the other is ionic, thereby generating suspended resin particles from about 0.05 micron to about 2 microns in volume diameter, followed by cooling the mixture to below the glass transition temperature of the resin of from about 45.degree. to about 65.degree. C., and subsequently aggregating the aforementioned suspended particles with an aqueous mixture of pigment, counterionic surfactant and optionally charge control additives to generate toner aggregates with an average particle volume diameter of from about 3 to about 21 microns, followed by heating the toner aggregates above the glass transition temperature causing coalescence of the toner aggregates to toner composites with an average particle volume diameter of from about 3 to about 21 microns. In embodiments, the present invention is directed to a process comprised of homogenizing a sulfonated polyester, such as one derived from about 42 mole percent to about 49.5 mole percent of a dicarboxylic diester monomer such as dimethylterephthalate, about 50 mole percent of a diol such as propylene glycol or diethylene glycol, and from about 0.5 to about 8 mole percent of a sulfonated difunctional monomer, such as dimethyl 5-sulfo-isophthalate sodium salt, in an aqueous solution containing at least two surfactants, one of which is a nonionic surfactant of from about 0.1 to about 5 percent by volume of an aqueous fraction such as polyethylene glycol nonyl phenyl ether, and the other or second surfactant is an ionic surfactant such as dodecyl benzene sulfonate sodium salt of from about 0.1 to about 1.5 percent by volume of the aqueous fraction in a heated pressurized vessel at high temperature of, for example, from about 120.degree. C. to about 170.degree. C., which vessel contains a Gaulin homogenizer, operated at from about 1,000 to about 10,000 revolutions per minute for a duration of from about 1 minute to about 3 hours, thereby generating suspended particles of from about 0.01 micron to about 2 microns in volume average diameter; followed by cooling the mixture to ambient temperature of from about 10.degree. C. to about 40.degree. C. and adding thereto a mixture comprised of from about 1 to about 10 percent by weight of pigment particles, such as carbon black, or other colored pigments like HELIOGEN BLUE.TM. or HOSTAPERM PINK.TM. in an aqueous mixture containing from about 0.1 to about 5 percent by volume of a counterionic surfactant such as alkylbenzene tetraalkylammonium chloride; followed by dispersing the resulting mixture and thereby obtaining suspended aggregate particles of from about 2 microns to about 21 microns in volume diameter; followed by coalescence of the aforementioned aggregated pigment-sulfonated polyester particles by heating to a temperature of from about 5.degree. C. to about 40.degree. C. above the glass transition temperature of the resin particle to generate toners with an average particle diameter of from about 3 to about 21 microns in volume average diameter. The aforementioned toners are especially useful for the development, especially xerographic development, reference U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference, of colored images with excellent line and solid resolution, and wherein substantially no background deposits are present.
In color reprography, especially process color reprography wherein pictorial images are generated, high gloss of from about 50 gloss units to about 80 gloss units as measured by the Gardner Gloss meter is highly desirable. Additionally, toners which fix onto paper at low fusing temperatures, such as from about 125.degree. C. to about 140.degree. C., are desirable to prolong the lifetime of the fuser and reduce its energy consumption. Accordingly, in order to satisfy the aforementioned high gloss and low fusing temperature requirements, it is advantageous to utilize conventional toners comprised of polyesters as the resin binder. However, the process for obtaining conventional toners usually requires the utilization of pulverization and cumbersome classification methods which are expensive, especially wherein small size toners of from about 3 microns to about 7 microns are desired. The toner process of this invention is directed to the economical preparation of toners containing, for example, polyester resins without the utilization of the known pulverization and attrition methods, and wherein a solvent is not needed, and wherein toners with an average volume diameter of from about 3 to about 7 microns can be obtained. Additionally, with the toners of this invention, high gloss of from about 50 to about 80 gloss units as measured by the Gardner gloss meter, and low fixing temperature of from about 125.degree. C. to about 150.degree. C. are attained in embodiments.
Certain in situ emulsion aggregation processes are known, and usually involve the use of polar emulsion resins, which are, for instance, comprised of an acidic functionality such as carboxylic acids or basic functionalities such as a tertiary or a quaternized amine to render the polymeric resin highly charged necessary for the controlled aggregation step with a pigment, by properly mixing the ionic and counterionic surfactants, followed by coalescence. The preparation of addition type emulsion resins with polar groups such as styrene acrylate-acrylic acid or methacrylic acid in the main chain wherein the acid group is from about 2 to about 8 percent of the polymer chain are known and utilized in the aggregation and coalescence step, wherein the resins have sufficient charge, such as mentioned in U.S. Pat. No. 4,996,127. However, such addition type polymeric resin is not effective for toner compositions wherein a low fixing temperature of from about 125.degree. C. to about 140.degree. C. is required with high gloss of from about 50 to about 80 gloss units as measured by the Gardner gloss meter, and nonvinyl offset properties such that the image does not offset to vinyl covers utilized in binding the images. Hence, there is a need for polyester based toner compositions wherein the aforementioned low fixing temperature, high gloss and nonvinyl offset properties are attained, and moreover there is a need for the preparation of toner by an economical in situ process which does not require the utilization of pulverization and cumbersome classification methods. Also, certain polyesters are considered neutral with low acid values present at the chain ends, and thus they usually do not provide the high polar charge necessary for proper aggregation control. In the present invention, a novel sulfonated polyester is utilized, wherein the sulfonated ion is present in the main chain of the polyester in an amount of, for example, from about 0.5 to about 8 percent by weight thereby providing adequate charging characteristics for effective use in in situ emulsion aggregation processes, and enabling the generation of toner particles comprised of sulfonated polyesters with a number of advantages, including a low fixing temperature of from about 120.degree. C. to about 140.degree. C., high gloss of from about 50 to about 80 gloss units as measured by the Gardner gloss metering unit, nonvinyl offset characteristics, and avoidance of charge control agents in embodiments.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of this '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Additionally, this process involves the preparation of emulsion addition type resins, such as that obtained from styrene, ethyl acrylate and the like, and wherein it is believed that polyesters cannot be effectively obtained. Also, note column 9, lines 50 to 55, wherein a polar monomer such as acrylic acid in the emulsion resin is necessary, and toner preparation is not obtained without the use, for example, of acrylic acid polar group, see Comparative Example I of the '127 patent. With the present invention, polyester resins are utilized, and more specifically sulfonated polyester emulsions with polar charges induced by the sulfonated ion groups, and wherein the emulsion particles are prepared by a high shear and high temperature processes. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70, are obtained. This process is thus directed to emulsion type resins and monomers therefrom, and coagulants are utilized. With the process of the present invention, addition type resins are avoided and sulfonated polyester resin particles are selected thereby enabling low toner fusing temperatures and high gloss with nonvinyl offset properties, and without the use of charge control agents. Similarly, the aforementioned disadvantages are noted in other prior art, such as U.S. Pat. No. 4,797,339, wherein there is disclosed a process for the preparation of toners by resin emulsion polymerization and spray drying; and U.S. Pat. No. 4,558,108, wherein there is disclosed a process for the preparation of a copolymer of styrene and butadiene by specific suspension polymerization processes. More specifically, the present invention is directed to a toner comprised of a sulfonated polyester resin prepared by an in situ emulsion aggregation, which sulfonated polyester is microsuspended to from about 0.05 to about 1 micron in volume diameter utilizing a high shearing device, such as a Gaulin homogenizer, at elevated temperature followed by cooling to ambient temperature, aggregating with pigmented particles and counterionic surfactant to toner size pigment-resin aggregated particles of from about 3 microns to about 7 microns in volume diameter as measured by the Coulter Counter, followed by heating the resulting aggregate composite above the glass transition resin of the polyester to effect coalescence and to generate toner particles of from about 3 to about 21 microns. These toners exhibit low fixing temperatures of from about 125.degree. to about 140.degree. C., high gloss of from about 50 to about 80 gloss units as measured by the Gardner Gloss device, excellent triboelectric charge induced, it is believed, by the sulfonated ion groups on the polyester resin, hence avoiding or minimizing the use of charge control agents.
Illustrated in U.S. Pat. No. 5,290,654 is an in situ process for the preparation of toner compositions which comprises dispersing a polymer, a pigment and an optional charge enhancing additive in an aqueous media containing a surfactant, or mixture of surfactants; stirring the mixture with optional heating to remove the organic solvent thereby obtaining suspended particles of about 0.05 micron to about 2 microns in volume diameter; subsequently homogenizing the resulting suspension with an optional pigment in water and surfactant; and followed by aggregating the mixture by heating thereby providing toner particles with an average particle volume diameter of from between about 3 to about 21 microns when said pigment is present. Disadvantages associated with this process include the use of solvents that can be toxic, which solvent is to be disposed of, or redistilled before reuse; thus, for example, adding to the process cost. Additionally, the polyesters of U.S. Pat. No. 5,290,654 do not contain sulfonated groups, hence are not polar charged and do not provide, it is believed, process latitude. Furthermore, with the sulfonated polyester of the present invention, excellent negative triboelectrification of toners with carriers are obtained, such as from about -10 to about -80 microcoulombs per gram, especially when the Xerox Corporation 9200 carrier comprised of, for example, a ferrite or steel core with a polymeric coating thereover of a terpolymer of styrene, methacrylate and an organosiloxane, and excellent admix properties are obtained, such as from about 30 seconds to about 2 minutes, without the use of charge control agents.
There is also disclosed in a Japanese Laid Open Patent H4-51251, a process for the preparation of polyester emulsion particles and toners comprised of a mixture of styrene based particles with polyester particles, however, the sulfonated polyesters of the present invention are not mentioned, and additionally pH adjusting agents must be utilized with the process of the H4-51251 patent and in situ toner particles comprised of exclusively a polyester resin with pigment and optionally charge control agent are not disclosed and cannot be obtained due to the nonpolar nature of the polyester utilized. The present invention discloses sulfonated polyester particles which are polar charged due to the sulfonated ions, and hence do not require pH adjusting agents during the process, and can be aggregated and coalesced with pigments and without the use of polar charged styrene based particles and without the use of charge control agents.
Water soluble sulfonated polyester resins are also known, such as illustrated in U.S. Pat. No. 3,564,008 wherein water-dissipatible sulfonated polyesters useful for sizing textiles, such as yarn, hemp rope and tie cord, are disclosed and wherein the polyester is derived from one dicarboxylic acid component, at least one diol component being a poly(ethylene glycol), and a difunctional monomer containing a metal sulfonate group attached to an aromatic nucleus. In the '008 patent, a sulfo-monomer component constitutes at least about 8 mole percent to about 45 mole percent of the polyester to achieve water-dissipatibility. Furthermore, sulfonated water-dissipatible polyester amides are disclosed in U.S. Pat. No. 3,779,993 which in addition to the polyesters of the '008 patent include amine monomers.
There is a need for a toner composition of low fixing temperature of from about 125.degree. to about 140.degree. C. with high gloss of from about 20 to about 50 gloss units and wherein toner offset to vinyl covers is avoided or minimized, and moreover there is a need for an economical in situ preparation without resorting to conventional pulverization and classification process. There is also a need for toner compositions containing no charge control agents to provide for excellent toner triboelectrification and admix properties. These and other needs are attained with this invention in embodiments by providing a toner composition comprised of a pigment, optionally a charge control additive, and a sulfonated polyester resin, and wherein the toner can be prepared from an in situ emulsion aggregation process as illustrated herein.